1. Field of the Invention
The present invention relates to a field emission display (FED), and more particularly, to a field emission display comprising a gate portion, a cathode portion, and an anode portion, in which the gate portion is provided with a metal mesh and a dielectric layer formed on at least one region of the metal mesh.
2. Discussion of Related Art
The FED comprises a cathode portion having a field emitter and an anode portion having a phosphor, which are opposite to and spaced apart from each other by a predetermined interval (e.g. 2 mm) and packaged in vacuum. In the FED, electrons are emitted from the field emitter of the cathode and collide with the phosphor of the anode, thereby displaying an image using the cathodoluminescence of the phosphor. Recently, the FED has been widely researched and developed as an alternative to a cathode ray tube (CRT). Here, the electron emission efficiency of the field emitter is significantly dependent on a device structure, an emitter material, and an emitter shape.
Currently, a field emission device can be largely classified into a diode type device comprising a cathode and an anode, and a triode type device comprising a cathode, a gate, and an anode. In general, the diode type field emission device is formed of diamond or carbon nanotube in a film shape. As compared with the triode type field emission device, the diode type field emission device has advantages that its manufacturing process is simple and the reliability of electron emission is good, however, has disadvantages in terms of electron emission control and driving voltage of field emission.
Hereinafter, the conventional FED will be described with reference to accompanying drawings. FIG. 1 is a schematic view illustrating a configuration of an FED having a diode type field emission device.
The conventional FED comprises a cathode portion that has cathode electrodes 11 arranged as a stripe shape on a bottom glass substrate 10B, and film type field emitter materials 12 provided on some regions of the cathode electrodes 11; an anode portion that has transparent anode electrodes 13 arranged as a stripe shape on a top glass substrate 10T, and phosphors 14 of red (R), green (G), and blue (B) colors provided on some regions of the transparent anode electrodes 13; and a spacer 15 to support the cathode portion and the anode portion to be opposite to and parallel with each other when they are packaged in vacuum. Here, the cathode electrodes 11 of the cathode portion and the anode electrodes 13 of the anode portion are aligned to cross each other so that one pixel is defined by each intersection therebetween.
An electric field required for electron emission in the FED of FIG. 1 is given by a voltage difference between the cathode electrode 11 and the anode electrode 13, and it is known that the electron emission typically occurs at the field emitter when an electric field of 0.1V/μm or more is applied to the field emitter material.
The FED of FIG. 2 is proposed to improve the drawback of the FED of FIG. 1, in which FIG. 2 schematically illustrates the configuration of the conventional FED employing a control device for controlling the field emitter corresponding to each pixel.
Referring to FIG. 2, the FED comprises a cathod portion that is provided on a glass substrate 20B and has scan signal lines 21S and data signal lines 21D formed of metal and arranged as a stripe form allowing electrical addressing to be carried out in a matrix, film type (e.g. thin film or thick film) field emitters 22 formed of diamond, diamond-like carbon, carbon nanotube or the like, which are provided in respective pixels defined by the scan signal lines 21S and the data signal lines 21D, and control devices 23 connected to the scan signal lines 21S, the data signal lines 21D and the field emitters 22 and for controlling field emission currents based on a scan signal and a data signal; and an anode portion that is provided on a glass substrate 20T and has transparent anode electrodes 24 arranged in a stripe form, and phosphors 25 of R, G, and B on some portions of the transparent electrodes 24; and a spacer 26 to support the cathode portion and the anode portion to be opposite to and parallel with each other when they are packaged in vacuum.
In the FED of FIG. 2, a high voltage is applied to the anode electrodes 24 to induce an electron emission from the film type field emitter 22 in the cathode portion, and to accelerate the emitted electrons with high energy. At the same time, if a signal of the display is inputted to the control devices 23 through the scan signal line 21S and the data signal line 21D, the control device 23 controls the amount of electrons emitted from the film type field emitter to represent row/column images.
The above-described diode type field emission device employed in the FED of FIGS. 1 and 2 does not require a gate and a gate insulating layer unlike the conical triode type field emission device, so that its structure is simple and easy to be manufactured.
In addition, the diode type field emission device has an extremely low probability in the breakdown of the field emitter resulted from the sputtering effect upon electron emission, so that it not only has high reliability of the device but also prevents the breakdown phenomenon of the gate and the gate insulating layer which is severely problematic in the triode type field emission device.
In accordance with the active matrix FED having the conventional diode type field emission device of FIG. 2, the control device 23 of the field emitter is employed in each pixel and a display signal is input via the control device, so that problems of high drive voltage of FIG. 1 along with non-uniformity of electron emission, cross talk or the like may be solved.
However, the FED which has employed the above-described field emission device has the following drawbacks.
In the FED having the diode type field emission device of FIG. 1, a high electric field required for the field emission (typically several V/um) is applied between the electrodes (cathode electrodes 11 and transparent anode electrodes 13 of FIG. 1) of both of the top and bottom substrates spaced apart from each other by a relatively long interval (typically ranged from 200 μm to 2 mm), so that a display signal should have a high voltage, which in turn causes an expensive drive circuit of high voltage to be required. In particular, although the voltage necessary for the field emission is decreased by reducing the interval between the top and bottom substrates in the FED having the diode type field emission device of FIG. 1, the anode electrode 13 is used as both a wiring line for the display signal and the electrode for accelerating electrons, so that it is impossible to implement the low voltage drive.
In the FED, a high energy of 200 eV or more are typically required to make the phosphor to emit light, and the luminous efficiency becomes higher as the electron energy increases, so that the high brightness FED can be achieved only when a high voltage is applied to the anode electrode. However, the high voltage applied to the anode electrode 24 and used for both the field emission and the electron acceleration induces a relatively high voltage to the control device 23 of each pixel, and is like to cause the breakdown of the control device when a voltage exceeding the breakdown voltage is induced to the control device 23.
Accordingly, the voltage applied to the anode electrode 24 is limited according to the breakdown characteristic of the control device 23, and the limited anode voltage causes a difficulty in manufacturing the FED having high brightness.